Category Archives: twin wall flue pipe

Do you need to line your chimney? Part 2

Do you need to line your chimney?

Building regulations do not say that it is essential to fit a flexible flue liner. If a chimney can be proven to be in good order then you do not have to fit a flexible flue liner.

ChimFit say that to really try and put you off from choosing not to fit a flexible flue liner. A wood burning stove that is designed to work with a 6 inch flue will not perform as well if it were attached to a chimney of 11 inch diameter!

With a flexible flue liner fitted properly, insulated (if required) there should be no reason for a wood burning stove not to perform perfectly.

The only time ChimFit may not recommend chimney liners is if the chimney is new.

Possible problems of deciding not to fit a ChimFit recommended flexible flue liner

1. If the chimney is not in good working order then smoke and harmful Carbon Monoxide can travel into your home, this is very dangerous since Carbon monoxide can kill and does kill. Note: that’s why a Carbon monoxide detector in all bedrooms as well as the room with the stove is highly recommended by ChimFit.

2. Hot air and gas rises – cool it down and it will slow its assent, stop altogether or sink. Hot air or gas does not rise well in cold chimney spaces, especially where heat-stealing space or rough surfaces are in the chimney as they steal heat and slow down the deposits that travel with the gases. These deposits, when slowed, form tar and condensation both of which can damage the innards of the chimney. If smoke slows down too much then the flow of said smoke starts to build up and dams underneath, thus the stove begins to burn inefficiently.

What to Know When Installing Flue Liner – Chimfit

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Most of our customers here at chimfit fit their stove and or flue liner themselves. You do not have to use a professional installer if you are DIY savvy and have general competence, If you are installing the wood burning stove into an fireplace and not installing a new chimney liner then the installation is very straightforward. Installing a chimfit flexible chimney liner or complete twin wall flue system is a larger project and may involve ladders/scaffolding if your roof does not have external access, this is since it is needed for the job, is still is however technically straightforward. Our twin wall chimney system simply slots together, no specialist knowledge or skills are required.

If you are thinking of completing the work yourself then you should contact the local council Building Control, they can then inspect the work you have done and sign it off if it is up to standard. Alternatively if the work is done by a professional installer (Which we here at Chimfit recommend) who is accredited by one of the relevant Competent Persons schemes such as HETAS then they can sign off their work themselves.

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Old houses will usually have exposed brick inside the chimney so it is not a legal requirement to line these older chimneys with chimfits liner unless they are broken or leaking, there are often advantages to lining such as increased draw. Installation of a wood burning stove and/or new flue system would not usually have anything to do with the local planning authority. If your property is a Listed Building then permission may or may not be required. If you intend your new chimfit flue pipework to run up the outside of an external wall then depending on the position you may need to check with the local Planning Department.

twin wall flue pipe

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Installing a wood burner boiler stove or other heating appliance and planning to run your flue system through a wall or a floor, you will need to use a twin wall flue system.

Twin wall flues have a 1 inch of insulation around the inner layer pipe. The external diameter of twin wall pipe is two inches larger than the internal, which is the quoted diameter. This is due to the internal diameter being a crucial figure when drawing and designing a wood burner flue system, you should always keep in mind of this when installing, for instance if you were to be careless and purchase a 5 inch diameter twin wall pipe the external diameter will be 7 inches it could very well be too big for the install!

If you are passing through a wall you must always set it at the maximum angle of 45 degrees and also use a wall sleeve. You can finish the job off with finishing plates. If you are passing through an internal floor in your home you will need to use fire stop plates and remain at least 50mm away from combustible materials like joists.

Always have at least one length of single wall enamelled stove pipe as you cannot connect your twin wall pipe directly to your wood burner’s flue. It is then possible to use single wall pipe internally, we recommended that you do not go more than 1.5 meters before changing to twin wall but you certainly need to convert at least 4 inches before passing through a wall or floor. You should use an adaptor to single wall to allow you to convert to twin wall flue pipe and then once you have converted you must continue the flue system in twin wall.